The invention relates to a torsion vibration damper, more particularly for motor vehicle clutch discs, with at least one preliminary damper acting in a predetermined angular area and having energy accumulators of lower stiffness, and at least one main damper acting in a predetermined angular area and having energy accumulators of greater stiffness, wherein the energy accumulators are active between the respective input and output parts of the preliminary and main dampers, and the output part of the torsion vibration damper is a hub provided with inner profiled sections to fit onto a gearbox shaft, as well as a flange forming the output part of the main damper is provided with inner profiled sections so that the inner profiled sections engage with the outer profiled sections of the hub and through this profiling the flange of the main damper is able to execute restricted relative rotation relative to the hub, as well as having at least one disc part which forms the input part of the main damper and holds the friction linings, and with at least one friction device.
Torsion vibration dampers with preliminary and main dampers having associated friction devices are known for example from DE 40 26 765 which each have a separate friction device for the main and for the preliminary damper, wherein the preliminary damper has a two-stage friction build-up and two-stage mounted energy accumulators for adapting to the different conditions. The drawback with this type of torsion vibration damper is the inability to dampen by simple means the torsion vibrations of the pressure plate at high speeds, such as occur for example during engagement and disengagement processes, so that the turning path of the preliminary damper is exceeded and the preliminary damper strikes against its restricting stop and thereby causes clutch noises which cannot be tolerated. Furthermore a construction of this kind is relatively complicated and the assembly becomes correspondingly expensive through the numerous structural elements used, which is all the more apparent if additional measures have to be used to counteract the clutch knocking previously described.
The object of the present invention is therefore to produce a torsion vibration damper of the kind mentioned above which provides the possibility of damping large torsion vibration amplitudes at high speeds, uses a minimum number of component parts and allows simple assembly.
According to the main claim this is achieved in that a torsion vibration damper, more particularly for motor vehicle clutch discs, is provided having at least one preliminary damper acting in a predetermined angular area and having energy accumulators of lower stiffness, and at least one main damper acting in a predetermined angular area and having energy accumulators of greater stiffness, wherein the energy accumulators are active between the respective input and output parts of the preliminary and main dampers, and the output part of the torsion vibration damper is a hub provided with inner profiled sections to fit onto a gearbox shaft, as well as a flange forming the output part of the main damper is provided with inner profiled sections so that the inner profiled sections engage with the outer profiled sections of the hub and through this profiling the flange of the main damper is able to execute restricted relative rotation relative to the hub, as well as having at least one disc part which forms the input part of the main damper and holds the friction linings, at least one friction device, wherein a spring which engages in the outer profiled sections of the hub is provided and controls at least one part of the friction device and defines the friction engagement.
It is thereby advantageous to make the hub two-part wherein an additional hub part with outer profiled section can hold the inner profiled section of the spring, as well as to provide a restricted relative rotation forming a free angle between the spring and the hub whereby the spring is entrained with the input part and thus a friction moment does not occur in the normal active area of the preliminary damper, that is friction is delayed until the free angle is used up and a high friction gradient, a so-called friction jump, ensues through the inner profiled section of the spring stopping against the outer profiled section of the hub.
Furthermore it is advantageous to set up the relative rotation between the spring and hub so that a delay with a free angle a is caused between the spring and hub, wherein this free angle a is the range from xc2x12xc2x0 to xc2x13xc2x0, preferably xc2x12.5xc2x0.
To perform its function as a control element of the friction device the spring has in a preferred embodiment an inner profiled section complementary with the external profiled section of the hub disc and forming teething with the external profiled section of the hub disc to thereby allow the said free angle.
Advantageously one design form has the preliminary damper arranged with its input and output part so that the output part of the preliminary damper is connected rotationally secured with the hub and the spring is tensioned between the input part of the preliminary damper and the disc part and/or a component part fixedly connected thereto. For design reasons in a further embodiment it is proposed that the previously mentioned component part connected fixed to the disc part is a second disc part set apart by spacer bolts and on which to optimise the friction coefficients a friction ring is fixed with which the spring forms the friction face.
The advantageous construction of a further embodiment of the spring is produced where the spring has an external profiled section with at least one radially outwardly pointing tongue wherein advantageously several tongues are provided which are spread out over the circumference and which have radially outwards an approximately semicircular recess. Double the number of friction tongues are now produced which form on the preliminary damper which is preferably designed as a friction face, an additional friction surface between the spring and preliminary damper.
In a further advantageous design the tongues are widened out at their radial outer side so that the friction face between the spring and tongues can be enlarged and the friction can thereby be improved.
Further advantageous design possibilities for optimising the friction surface between the spring and input part of the preliminary damper are offered wherein the input part of the preliminary damper has, on the axial side facing the spring in the area of the contact surface between the input part and the spring tensioned with a contact bearing angle xcex2, a rounded end which has a pitch angle such that the bearing angle xcex2 of the spring is approximately xcex2=0.
A further advantageous design relates to the input part of the preliminary damper which has at least one axially extending pin on the axial side facing the spring, wherein an arrangement of several pins spread uniformly over a circumference of constant diameter is advantageous and whose number corresponds to the recesses of the tongues formed on the outer circumference of the spring. It is further advantageous if the pins engage with play in the recesses of the tongues and thus serve for pre-centring during assembly. The play between the tongues and pins is thereby advantageously greater than the free angle of the teething between the spring and hub, so that the control of the friction device is not impeded. The pins can in further embodiments serve as stops for restricting the spring path.
Further advantageous design possibilities relate to the friction ring connected to the disc part and which in one design model is advantageously formed so that it is press-fitted into a bore provided in the disc part through at least one, and preferably several axially extending hollow pins spread evenly over the circumference, so that the friction ring is fixed on the disc part during assembly and is connected rotationally secured to the disc part.
In a further embodiment the friction ring has a ring located on the outer circumference and raised axially in the direction of the spring whereby its ring face drops advantageously towards its inner diameter and the ensuing ring face forms relative to the inner face of the ensuing ring a phase angle xcex3 which is advantageously designed so that the contact bearing angle xcex2 of the spring on the friction ring is approximately xcex2=0 and thus an improved friction surface is formed. The formation of the raised ring has the advantage that radially outside the outer circumference of the raised ring of the friction ring there is a further plate spring which belongs to a friction device of the main damper and which thereby is formed without taking up additional axial structural space. It is supported on one side on the non-raised inner ring face of the friction ring and on the other side on the axially aligned tabs of the control plate for the second stage of the main damper so that the friction ring forms at least a part of the friction device of the preliminary and main damper.
A further development of the invention relates to the arrangement and design of the preliminary damper for space-saving fitting of the spring engaging in the hub. Advantageous for this is an arrangement where the preliminary damper is housed axially between the disc part and a second associated disc part so that the spring can be tensioned directly between one of the two disc parts or a friction ring attached thereon and the preliminary damper. In principle however other design forms are possible wherein the preliminary damper has an axial stagger relative to the main damper and the spring is tensioned between the first disc part or a component part connected thereto and the input part of the preliminary damper. Furthermore the first disc part can be attached in the axial direction centrally on the hub whereby the preliminary damper and flange can be mounted axially on the same side or the disc part can be mounted flanked on both sides.
To fix the output part of the preliminary damper on the output part of the main damper in one embodiment it is proposed that pins attached to the output part of the preliminary damper are fitted into windows provided in the output part of the main damper for receiving the energy accumulators. These pins are provided complementary with the two radially inner corners of each window on the input part of the preliminary damper, are shaped out axially and are engaged in the corners of the windows. They simultaneously centre the preliminary damper on the output part of the main damper.
A further embodiment according to the invention relates to the design of the hub wherein the external profiled section of the hub is continued in a cone which has for this purpose a positive-locking inner profiled section or an axially mounted positive-locking profiled section and wherein the spring engages by its inner profiled section in an external profiled section of the cone. This solution produces a significant advantage with regard to assembly since through the variation of the cone which is simple to produce different free angles of the spring can be created without changing the hub or spring.